Data protection systems and methods

ABSTRACT

Systems and methods are provided for protecting electronic content from the time it is packaged through the time it is experienced by an end user. Protection against content misuse is accomplished using a combination of encryption, watermark screening, detection of invalid content processing software and hardware, and/or detection of invalid content flows. Encryption protects the secrecy of content while it is being transferred or stored. Watermark screening protects against the unauthorized use of content. Watermark screening is provided by invoking a filter module to examine content for the presence of a watermark before the content is delivered to output hardware or software. The filter module is operable to prevent delivery of the content to the output hardware or software if it detects a predefined protection mark. Invalid content processing software is detected by a monitoring mechanism that validates the software involved in processing protected electronic content. Invalid content flows can be detected by scanning the information passed across system interfaces for the attempted transfer of bit patterns that were released from an application and/or a piece of content management software.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/815,121 filed Jun. 14, 2010, now U.S. Pat. No. 8,510,849; which is acontinuation of U.S. application Ser. No. 12/142,688 filed Jun. 19,2008, now U.S. Pat. No. 7,770,031; which is a continuation of U.S.application Ser. No. 09/653,517 filed Aug. 31, 2000, now U.S. Pat. No.7,406,603, which claims priority to U.S. Provisional Application No.60/151,790 filed Aug. 31, 1999, all of which are hereby incorporated byreference in their entireties.

COPYRIGHT AUTHORIZATION

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF THE INVENTION

The present invention relates generally to systems and methods forprocessing electronic content. More specifically, the present inventionrelates to systems and methods for inspecting, classifying, controlling,and/or modifying the processing of protected electronic content toprovide enhanced resistance to attempts to circumvent contentprotection.

BACKGROUND OF THE INVENTION

Conventional content protection mechanisms typically focus on protectingcontent while it is being transferred between systems and/or while it isstored on a system. For example, some conventional techniques providemechanisms (with varying degrees of effectiveness) for securing thetransmission and/or storage media itself, thus preventing, or at leastresisting, malicious tampering or manipulation of the content. Othertechniques concentrate on protecting the content directly—as opposed tothe transmission and/or storage media—and make use of encryption andother technologies to make the content inaccessible, or at leastpractically unusable, while it is being transmitted or while it isstored.

A problem that arises, however, is that when content is released foruse—for example, when stored audio content is decrypted and/ordecompressed and played by a consumer—it is possible for an attacker tointercept the content and circumvent the content and/or transmissionprotection that was used. This is a serious problem, as most systemsmust remove the content protection at some point, since the content istypically of little use in its protected form.

One way to address this problem is to minimize the amount of time thatthe content is unprotected. For example, an audio file might bedecrypted and/or decompressed by obscure drivers immediately before itis sent to the system's speakers or other output devices. This approachis not foolproof, however, as an attacker might simply record the audiooutput being played by the speakers, thus obtaining an unprotected (orless protected) copy of the content, albeit of somewhat lesser qualitythan the original. A more serious attack intercepts the content while itis still in digital form, before it is output to the user. For example,an attacker might insert or substitute a malicious software driver tointercept the content file as it is headed for an output device. Themalicious driver might reroute and/or duplicate the unprotected contentfile, thus allowing the attacker to obtain a perfect digital copy of thecontent and/or to use the content in an unauthorized manner.

SUMMARY OF THE INVENTION

The present invention provides systems and methods for detecting anddefending against attacks such as those described above. Specifically,systems and methods are disclosed for protecting content from the timeit is packaged to the time it is released for use. It should beappreciated that the present invention can be implemented in numerousways, including as a process, an apparatus, a system, a device, or amethod. Several inventive embodiments of the present invention aredescribed below.

In one embodiment, systems and methods are provided for performingprogrammatic inspection and generation of signatures or otheridentifiers for identifying software drivers, system software modules,and/or system hardware. Techniques are disclosed for deriving asignature or other identifier that allows identification of certainsoftware modules based on behaviors such as their use of certain systemprogramming interfaces, linkage with certain modules (programdependencies), recognizable internal data structures (implementationstructure, constant data, etc.), opcode patterns (e.g., the structure ofgenerated code and/or instruction sequences), and so forth. Thesignature or identifier encodes a persistent means for programmaticallydiscriminating legitimate, known, and/or identifiable modules fromimpersonated, untrusted, and/or malicious modules. The technique mayalso be applied recursively to qualify program dependencies (e.g. thesignature of dependent modules which are linked by the top-level systemsoftware module or software driver). Analysis may be used to qualify aconfiguration of multiple modules which form a qualified dependencygraph.

In another embodiment, systems and methods for protecting contenttransfers are provided. Techniques are provided for locating a contentsignature or identifier in protected content, then filtering certainsystem programming interfaces (such as file writing interfaces) toprevent transfers of content, or to apply modifications to content,containing those signatures or identifiers. In a preferred embodiment,the content signature comprises a distillation (e.g., a secure hash orthe like) of one or more parts of a protected content object, and isderived from the content itself. System interfaces that can be used totransfer or copy content to an inappropriate destination (e.g., files,network ports, etc.) are filtered by examining the data passing acrossthose interfaces for the signatures or identifiers of protected content,and when a signature is found that indicates that content is beingtransferred inappropriately, the operation can be disallowed or thecontent can be modified in a predefined manner. The content signaturemechanism is optimized for rapid scanning to locate signatures withinlarge sequences of data. One or more signatures may be employed for agiven protected content stream.

In another embodiment, systems and methods are provided for performing adiscretionary, policy-based configuration and validation of systemssoftware and drivers. Techniques are disclosed which allow anapplication to inspect systems software upon which its data processingis dependent, and which enable the application to determine based on aset of “rules” or policy controls whether it will allow, modify, ordisallow downstream processing operations on protected content. Thisprocess can be advantageously implemented without dependency on, andregardless of any operating system support for, cryptographically signedcode or access control mechanisms. For example, this process can beimplemented under the control of the application itself, or under thecontrol of trusted management or digital rights management (DRM)software with which the application is linked. The aforementionedpolicies and techniques can be flexible, and may vary betweenapplications. For example, an application may specify that alldownstream processing modules must be marked as “trusted” using acryptographically-derived credential. Alternatively, or in addition, theapplication may specify that only modules that satisfy certain criteriaregarding the correct use of certain system API functions areacceptable. In some embodiments, operations may be modified, rather thansimply disallowed, in order to change the value of the content (data)that they process—for example by modifying the content to reduce oreliminate its commercial value (such as by inserting noise, or bydamaging the format), to insert a special mark (such as a specialwatermark identifying the content as stolen), or other appropriatetechniques.

In yet another embodiment of the present invention, a protection systemis provided for controlling protected data/content processing andtransfer based on inspection and/or qualification of dependent systemsoftware, drivers, and or hardware. System drivers, software, and/orhardware are inspected to determine whether electronic content can beprocessed by those drivers, software, and/or hardware. This process iscontrolled by the application management software which is linked withthe application, or by a digital rights management (DRM) system linkedwith the application and responsible for protecting the contentaccording to a set of rules or policies. The decision as to whether thesystem software, drivers, and/or hardware may process the content, orwhether certain modifications should be applied to the content as it isprocessed, is based on a qualification or inspection techniqueimplemented by a separate process that is operable to check thesignature or cryptographically-derived identity of the system software,drivers, and/or hardware. In one embodiment, the determination ofwhether content may be processed or modified is independent ofmechanisms or services such as file names of program files whichimplement system software or software driver code, and is alsoindependent of cryptographically signed code and native operating systemaccess control mechanisms or services provided by the operating systemor system software itself.

In some embodiments, the determination of whether content may beprocessed is made using multiple qualification techniques to establish aconfidence factor regarding the trustworthiness or security of thedependent system software, drivers, and/or hardware. Evaluation of theconfidence factor is under control of the application or its associatedmanagement or DRM system. The application or its management software mayspecify a default interval for ongoing qualification of the dependentsoftware in order to thwart tampering and/or replacement of theconfigured system software or drivers. Alternatively, the application orits related management software may register for asynchronousnotification of changes detected by a separate, trusted qualification orinspection process running on its behalf, or by a notification facilityin the operating system itself. In yet another embodiment, theapplication or its related management or DRM software may poll aninterface implemented by the separate, trusted qualification orinspection process.

In one embodiment, techniques are provided for maintaining thenon-circumventability of the qualification or inspection mechanism, andfor providing the application or its related management software withthe ability to detect the presence or removal of the inspectionmechanism on a periodic basis, thereby creating an “interlock” mechanismthat assures the presence or non-replacement of the correct version ofthe trusted qualification or inspection software. Thus, an effectivelymandatory protection system can be provided which must be satisfiedwithin the policy-based confidence factor in order for correctprocessing of the protected content to occur. In one embodiment, thepolicy and confidence factors may evaluate to simple boolean values.

These and other features and advantages of the present invention will bepresented in more detail in the following detailed description and theaccompanying figures which illustrate by way of example the principlesof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings,wherein like reference numerals designate like structural elements, andin which:

FIG. 1 illustrates a system for practicing an embodiment of the presentinvention.

FIG. 2 is a more detailed illustration of a system for practicing thepresent invention.

FIG. 3 is a block diagram of a system and method for fingerprintingcontent files.

FIGS. 4A and 4B are flow charts illustrating methods of inspectingdrivers, software, and/or hardware modules.

FIG. 5 is a block diagram illustrating a system and method forprotecting content by performing inspections of drivers, software,and/or hardware modules, and by using the inspection results inconjunction with predefined policies to control processing and/or use ofthe content.

FIG. 6 is an illustration of the application of a policy for processingcontent in light of system characteristics.

FIGS. 7A and 7B are flow charts illustrating the operation of a contenttransfer manager and a content transfer monitor in accordance with anembodiment of the present invention.

FIG. 8 illustrates a content transfer protection mechanism in accordancewith an embodiment of the present invention.

DETAILED DESCRIPTION

A detailed description of the invention is provided below. While theinvention is described in conjunction with several embodiments, itshould be understood that the invention is not limited to any oneembodiment. On the contrary, the scope of the invention is limited onlyby the appended claims and encompasses numerous alternatives,modifications, and equivalents. For example, while several embodimentsare described in the context of a system and method for protecting audiocontent, it should be appreciated that the disclosed systems and methodsare readily adaptable for broader application. For example, withoutlimitation, the present invention could be readily applied in thecontext of video, image, text, audio-visual, or other content types. Inaddition, while numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of the presentinvention, the present invention may be practiced according to theclaims without some or all of these details. Similarly, for the purposeof clarity, certain technical material that is known in the art has notbeen described in detail in order to avoid obscuring the presentinvention. For example, in the following discussion reference is made toa number of terms, concepts, and techniques that are well-known in thefields of computer architecture, computer programming, and cryptography.Information on computer architecture and computer programming can befound, for example, in Hennessy et al., Computer Architecture: AQuantitative Approach, 2d ed. (Morgan Kaufmann 1996); Patterson et al.,Computer Organization and Design: The Hardware/Software Interface, 2ded. (Morgan Kaufmann 1997); Microsoft Windows NT Device Driver Kit:Kernel-mode Driver Design Guide (Microsoft 1993); Dekker et al.,Developing Windows NT Device Drivers: A Programmer's Handbook(Addison-Wesley 1999); Born, Inside the Registry for Microsoft Windows95 (Microsoft Press 1997); Baker, The Windows NT Device Driver Book(Prentice Hall 1997); and Solomon, Inside Windows NT, 2d ed. (MicrosoftPress 1998). Information on cryptography can be found, for example, inMenezes et al., Handbook of Applied Cryptography (CRC Press 1996) andSchneier, Applied Cryptography, 2d ed. (John Wiley & Sons 1995).

The following patents and applications, each of which is assigned to theassignee of the current application, are hereby incorporated in theirentirety by reference: Ginter et al., “Systems and Methods for SecureTransaction Management and Electronic Rights Protection,” U.S. Pat. No.5,915,019, issued Jun. 22, 1999 (“the '019 patent”); Ginter et al.,“Trusted Infrastructure Support Systems, Methods and Techniques forSecure Electronic Commerce, Electronic Transactions, Commerce ProcessControl Automation, Distributed Computing, and Rights Management,” U.S.patent application Ser. No. 08/699,712, filed Aug. 12, 1996 (“the '712application”); Van Wie et al., “Steganographic Techniques for SecurelyDelivering Electronic Digital Rights Management Information OverInsecure Communications Channels, U.S. Pat. No. 5,943,422, issued Aug.24, 1999 (“the '422 patent”); Ginter et al., “Systems and Methods forSecure Transaction Management and Electronic Rights Protection,” U.S.Pat. No. 5,892,900, issued Apr. 6, 1999 (“the '900 patent”); Shear etal., “Cryptographic Methods, Apparatus and Systems for Storage MediaElectronic Rights Management in Closed and Connected Appliances,” U.S.patent application Ser. No. 08/848,077, filed May 15, 1997 (“the Shearapplication”); Collberg et al., “Obfuscation Techniques for EnhancingSoftware Security,” U.S. patent application Ser. No. 09/095,346, filedJun. 9, 1998 (“the Collberg application”); Shear, “Database UsageMetering and Protection System and Method,” U.S. Pat. No. 4,827,508,issued May 2, 1989 (“the Shear Patent”); and Sibert, “Systems andMethods for Using Cryptography to Protect Secure and Insecure ComputingEnvironments,” U.S. patent application Ser. No. 09/628,692, filed Jul.28, 2000 (“the Sibert application”).

The present invention relates generally to computer processing ofprotected digital content by applications and supporting operatingsystem services implemented by kernel mode or user mode modules, alsoknown as drivers or filters, respectively. The invention provides a setof services for inspecting, classifying, controlling, and modifying thefunctionality of the operating system modules according to the securitypolicies of an application and/or a digital rights management (DRM)system linked with the application and responsible for ensuring thesecure processing of digital content. The invention provides anextensible set of functions for protecting against the unauthorized useof digital content by enabling the application and/or its associated DRMsystem to restrict processing of, or to impose modifications to, thecontent depending on whether system modules are present which do notconform to the security policies of the application or DRM system. Suchnon-conformance can be determined by a variety of techniques, includingwithout limitation, inspection, classification, and/or control of amodule's dynamic behavior, static structure, and/or other identifyingcharacteristics.

The present invention provides systems and methods for protectingdigital content from the time it is packaged until it is experienced bythe consumer. In one embodiment, a combination of watermarking andfingerprinting is used. The content producer pre-processes the contentin order to obtain the information needed to enable transaction-timewatermarking or fingerprinting at the consumer system (as described inmore detail below). A watermarking technology is used to embedimperceptible codes into the content as it is being released to theconsumer. The embedded information may identify not only the owner ofthe content, but also the individual who purchased or otherwise releasedthe content. Thus, if the content is stolen and packaged in a file, oreven re-recorded, it will retain a mark indicating who was responsible.Although watermarks are applied digitally, the advanced signalprocessing techniques on which they are based ensure that they can berecovered even after one or more analog processing steps are applied tothe content. Multiple watermarking technologies may be used, thus givingcontent providers a variety options.

In another embodiment, protection against content misuse is provided byencryption, watermark screening, detection of invalid content processingsoftware and hardware, and/or detection of invalid content flows.Encryption protects content that is delivered over theeasily-intercepted RPC channel between the management software,application software, and the libraries that they use. Encryptionprovides secrecy, so that content cannot be intercepted and used, andalso ensures that the RPC requests cannot be usefully modified intransit (modification might permit, for example, circumvention of anapplication's specified intentions). Watermark screening is provided byinvoking a filter module to examine content before it is delivered tothe output hardware. The filter module is operable to prevent deliveryof the content if it detects a predefined protection mark. Invalidcontent processing software is detected by a monitoring mechanism. Forexample, when protected content is released by an application, asecurity monitoring module continuously validates that the softwareinvolved in processing the content (i.e., drivers, filters, etc.) willnot misuse it. As described below, this validation can be performed by acombination of techniques that detect invalid software modules (such asAudioJacker) and/or ensure that known or validated software is present(such as legitimate drivers for audio cards). Invalid content flows canbe detected by scanning information passed across file system interfaces(and/or other communication interfaces) for the attempted transfer ofbit patterns that were released from the application and/or managementsoftware. For example, in one embodiment this technology looks forpredefined “signatures” during file system operations.

FIG. 1 illustrates a system for practicing an embodiment of the presentinvention. As shown in FIG. 1, a typical computer system 100 includes avariety of interconnected components. For example, computer system 100may include a personal computer 101, having a monitor 102, keyboard 104,mouse 106, speakers 108, hard disk drive 110, floppy disk drive 111, andCD-ROM drive 112. In addition, computer 101 may be capable of connectingto, or interacting with, printer 114, modem 116, facsimile machine 118,scanner 120, personal digital assistant (PDA) 122, external disk storage124, and/or an ethernet (or other network) interface card (not shown).In addition, computer 101 may use modem 116 and/or a network interfacecard to interact with other computers 130, printers 132, storage media134, and/or other peripheral devices connected to a network 136, such asa local area network (LAN) or the Internet. One of ordinary skill in theart will appreciate that the present invention can be practiced onsystems that include only some of the components shown in FIG. 1, andcan also be practiced on systems that use a variety of devices that arenot shown in FIG. 1, including without limitation portable audioplayers, portable video players, digital cameras, video-cassetterecorders (VCRs), and/or camcorders, to name just a few examples.

The operation of computer 101 is typically controlled by computerhardware operating under software control. In addition, the user ofcomputer 101 can control its operation using, e.g., keyboard 104 andmouse 106, and can cause computer 101 to access digital content filesstored on other devices in computer system 100. Once these files areaccessed, the user can instruct computer 101 to process the files and/orsend them to other devices in system 100. For example, a user mightdownload an audio file from networked computer 130 and store the file onhard disk 110. Later, the user may access the file from hard disk 110and cause it to be played on speakers 108, or downloaded to PDA 122, toname just a few illustrative examples of the operations a user mightchoose to perform.

As shown in FIG. 2, computer-implemented processing of digital datatypically entails the collective operation of multiple software andhardware systems. The software systems involved in this processingtypically include some or all of the following:

-   -   Firmware 202, comprising basic input-output software or BIOS,        often implemented in read-only, persistent memory such as ROM,        PROM, EPROM, or flash memory;    -   Operating system (OS) software, typically comprising a set of        kernel mode modules and/or user mode modules;    -   Libraries 210, typically comprising reusable modules, provided        by the operating system developer or other parties, to implement        common processing operations on files, databases,        communications, and the like;    -   Services, typically including programs that support processing        for multiple applications, such as print spoolers, databases,        web servers, middleware communications processes, and so forth;        and    -   Application programs 214 that implement processing for        particular user activities such as editing a document, viewing a        web page, playing a song or a movie, entering data into a form,        or a virtually limitless set of other uses.

Not every computer system distinguishes between user mode 208 and kernelmode 206, although most systems do. If the distinction is important tothe operating system, it is usually implemented with CPU support. Forexamples, the Intel 80×86 architecture provides hardware support for adistinction commonly referred to as the hardware ring protectionarchitecture. The ring protection architecture enables kernel modemodules (sometimes referred to as supervisor mode modules) to operate ina hardware-protected ring (ring zero), and user mode modules to operatein a different ring (ring three). Ring three modules typically cannotdirectly call functions, or access program memory, associated with ringzero modules without using a hardware-supported ring transition gatefeature. The transition gate feature is typically managed by ahigher-level operating system abstraction, such as a system “trap” or“thunk” call, that packages program stack data on one side of thetransition gate according to the rules of the operating system andhardware (implemented as a hardware interrupt or as a reservedinstruction, depending on the CPU), and invokes execution on the otherside of the transition boundary. Other processors provide techniques foraccomplishing similar functions as do other operating systems such asUnix. For purposes of practicing the present invention, however, it isnot directly material whether a given operating system and processorcombination support a formal protection scheme that distinguishesbetween user mode and kernel mode processing. The present invention canbe implemented regardless of this distinction, although the presence ofthe distinction is relevant to embodiments where kernel modeimplementation techniques and user mode implementation techniques arecoordinated across the transition boundary.

User and kernel mode operating system modules, libraries, services, andapplications normally import and/or export some set of applicationprogramming interfaces (APIs), which are the interfaces that enable thecomputer software system to be constructed by many different people, indifferent places, and at different times. The term software “module”refers generally to a piece of software that has been packaged—usuallyusing techniques specific to a given operating system and its supportedprogram linkage and loader rules—as a set of binary instructions for aprocessor (or a machine that emulates a processor) to implement acomputer program running either as part of the operating system or assoftware layered on top of the operating system. Standard module formatsvary according to the operating system (and its linkage/loader rules),and packaged binary instructions also vary according to the supportedprocessor. Standard formats include the .ELF and .ELF64 formats for Unixsystems, and the PE .DLL format for newer Microsoft operating systems.In addition to using (i.e., importing) or implementing (i.e., exporting)APIs, modules may also register for and process specific software orhardware interrupts.

Complex programs can be constructed from multiple modules, eitherstatically at compile/link time when the programmer creates the program,or dynamically at runtime when the end user runs the program. Relevantcharacteristics of software modules include:

-   -   the ability to determine imported APIs (e.g. the ability to        inspect a subject module in order to identify its dependencies        on other modules);    -   the ability to determine exported APIs (e.g. the ability to        determine if other modules can call or replace functions        provided by a subject module);    -   the ability to inspect static binary program structure;    -   the ability to monitor dynamic binary program operation of a        subject module through observation of API calls, software        interrupts, hardware interrupts, and/or operating system        messages and events implemented by that module in cooperation        with other modules; and/or    -   the ability of third-party code to introduce itself into the        running binary program address space of a subject module and to        replace functions implemented by that module.

The ability to determine imported APIs makes it possible for a developerequipped with the correct tools (such as common commercial developmenttools for the Windows operating system, including, for example,Microsoft's Visual Development products) to inspect a program anddetermine whether it uses certain operating system modules, libraries,etc. Examples of such programs include the Microsoft “Depends” programand DumpBin. This technique can be used to reverse engineer programstructures for the purpose of debugging, replacing, and/or augmentingthe function of in-place programs. Sound use of the technique enablesdevelopers to augment the functions provided to a program by creating“shim” or “wrapper” modules which extend the normal calls of dependentprogram modules. Using a technique commonly referred to as moduleinterception, a skilled programmer can create a shim or wrapper modulethat masquerades as the original subject module and implements its APIsfor the purpose of intercepting an API call ahead of the subject module.By using the API calls, parameters, and return values, the programmercan create a replacement for the original module and name it in such away that the replacement code is called in place of the original code.The replacement code receives all calls for the original program, andcan either handle them directly, or selectively pass them on to theoriginal as its surrogate. Intercepting the calls allows themasquerading program to perform additional processing, which in somecommercial examples allows for management, auditing or accountingfunctions, and/or connection with other networked systems.

Using a technique often referred to as module substitution, a skilledprogrammer can replace a known module with a substitute that implementsthe same API functions differently for purposes such as capturingprotected data or information about the user. Module interception andreplacement techniques can be used in conjunction with modules in eitherkernel mode or user mode processing. Current mass-market commercialoperating system products provide no systematic support for preventingeither module interception or module substitution in kernel mode or usermode code. Some networking and system management products supportconfiguration control for workstation and server systems which may beuseful for correcting the effects of module interception or modulesubstitution relative to a baseline configuration established by asystem administrator. Although such programs are useful in enterprisesettings, they generally are not implemented in the consumermarketplace.

The ability to determine exported APIs makes it possible for a developerusing common, commercially-supported tools, to inspect functions thatthe module implements for other programs, and to implement differentversions of those interfaces. This technique is often referred to as APIredirection. API redirection is widely used in commercial networking andmanagement programs for product features that allow the end-user toconfigure file system networking and other useful administrationfeatures. API redirection can be used by any skilled third party,however, and can also be used to redirect functions for maliciouspurposes such as capturing private information about the user, protecteddata, and so on.

The ability to inspect the static structure of a program binary makes itpossible for another program to potentially determine the logic of thesubject program—program disassembler tools commonly provide thiscapability. More importantly, this technique makes it possible toidentify patterns on a per module basis that uniquely identify thesubject program and its dependent parts, thereby making it possible todistinguish the subject program from unauthorized substitutes.

The ability to create a program that can observe the API calls, softwareand hardware interrupt processing, messaging, and event behaviors ofanother subject program builds on the ability to determine imported andexported APIs, and the ability to distinguish interesting subjectprograms for discrete observation (such as a known module from a likelyreplacement module). Program debugging and performance tools oftenimplement techniques for tracing an API call invoked on one module ontoother dependent modules and potentially other API calls. In addition toinstrumenting API calls, it may also be important for a monitor programto optionally track and instrument hardware and software interrupt (IRP)functions. Embodiments of the present invention apply the general APIand IRP instrumentation techniques to programmatically discriminatecalling paths of known good modules from those of potential replacementmodules. Additionally, embodiments of the present invention are capableof detecting efforts to inspect and tamper with memory structures suchas program buffers in RAM or on peripheral hardware, where protecteddigital content might be stored during processing (often referred to asmemory snooping). When a replacement module is identified, thetechniques of the present invention can be further employed to determineif the replacement module's observed dynamic behavior invokes APIs whichwould otherwise indicate behaviors inconsistent with the policy of thetop-level controlling application (such as saving a file to storage ordirecting it to processing which is not part of the normal programbehavior).

The ability to dynamically observe certain program behavior also makesit possible to identify whether an attempt is being made to introducemodifying code into the address space of another module. Techniques forimplementing this type of behavior are sometimes referred to as codeinjection, and have been explained in press articles regarding theWindows operating system family (some operating systems make this typeof behavior virtually impossible due to operating system-supported andhardware-enforced address space protection guarantees). Virus protectionsystems often incorporate a variety of techniques for detecting similartypes of malicious attacks. These techniques generally rely on theability to identify a specific program module along with its importedand exported APIs, and/or to trap and redirect interrupt processingprovided by the host operating system. The ability to identify modulesalong with their imported and exported APIs, and also to be able toinstrument these APIs for monitoring functions, provides a basis forbeing able to identify code which may attempt to modify the behavior ofa known good module through address space code injection.

Referring once again to FIG. 2, when a computer processes digitaldata—for example a song in the form of a digital audio data-stream—arelatively large amount of the software in the computer system may becalled into use. For example, application software 214 may appear to theuser as a music player, providing an interface to select songs from aplay list using controls represented as buttons. Another program may becalled by player application 214, e.g., digital rights management (DRM)program 216, to check and enforce a set of policies or rules associatedwith the song—e.g., to determine whether that specific user isauthorized at that time to play, or to perform some other action on, thesong.

In addition, the operating system will typically be used to run bothapplication 214 and DRM program 216, possibly as separate processescomposed of multiple threads. The operating system may also enableapplication 214 and DRM program 216 to communicate via API calls withboth user mode and kernel mode modules, and to perform operations onlocal disk storage subsystem 218 or across a network in order to, e.g.,assemble play lists or the like. In addition, the operating system maybe used to dynamically load additional program modules that may beneeded to run parts of the application or other subsystems used by theapplication.

Driver software 220, which is commonly implemented as kernel modemodules, may also be called into service by the operating system. Driversoftware 220 commonly invokes additional BIOS-provided software tointeract with certain hardware that forms part of the computer itself.For example, driver software 220 may be used by application 214 and DRMservice 216 to communicate requests to open, read, write, and closefiles to the physical disk device 219, and, when playing a song, tocommunicate with sound card 222 and to process the audio data. Disk,keyboard, video, mouse, and audio devices, as well as external busessuch as the Universal Serial Bus or a SCSI bus, are each controlled byone or more drivers which are typically organized into processingchains, such as processing chain 224. The operating system kernelprovides support for connecting drivers 220 b into chains, and forconnecting the head-ends of these chains to code which implements thekernel/user-mode transition and the connection to user-mode filters 220a and libraries.

In an idealized scenario, the code that runs on the system is providedby reputable vendors and is well-designed, tested,functionally-consistent, and specific to the purpose of its part of thesystem. For example, an audio sound card vendor may supply aninstallation program and possibly multiple kernel-mode drivers anduser-mode applications for configuring and using the sound card. Diskdriver manufacturers and video card manufacturers generally do the samefor their respective components.

However, the real world is not so ideal, and in fact the very complexityand modularity of the system makes it possible for a number of behaviorsto exist that subvert or modify the intended design and operation of thesystem. For example, as described above, techniques that can beexploited for these purposes include API redirection; software andhardware interrupt processing redirection; module interception; modulesubstitution; memory snooping in system RAM; memory snooping in othermemory address spaces (e.g., system peripheral hardware); interception,redirection, and suppression of operating system messages and events;redirection of content to an unapproved I/O port or bus; injection ofmodifying program code into another program address space; and a varietyof other techniques.

Embodiments of the present invention are operable to establish functionsfor monitoring system behavior and for detecting suspicious or directlymalicious threats to the processing of digital content. These techniquesare effective against the listed threats, and may also be useful againstother threats still to be identified—which is an importantcharacteristic, since it is advantageous for a system to be able to dealwith new attacks as they arise.

Returning to the example of an audio player, several of the threatsenumerated above have actually been used to attack digital audiocontent. For example, the A2B2WAV program was designed to inject codeinto a user-mode audio player, the code being operable to add a buttonto the audio player's graphical user interface which enabled users tosave protected content in an unauthorized and unprotected form. TheA2B2WAV program redirected protected content by inserting itself intothe application calling chain, and by sending the resulting content tofile storage. The present invention provides systems and methods fordetecting this type of technique, as the behaviors required toinstrument the user mode and kernel mode calling chains and to send thecontent to disk involve the use of API calls and interrupts that can beinstrumented for detection of inappropriate behaviors when digitalcontent is being processed.

Another example of an actual attack on digital audio content is theAudioJacker program. This program was designed to provide a substitutefor a known commercial audio driver. While masquerading as the driver,the AudioJacker program converts protected content to an unprotectedform and stores the result to disk. This type of attack is alsodetectable using embodiments of the present invention through theability to distinguish the substitute driver from the known good driver,and/or by instrumenting other API and interrupt processing functions inorder to detect behaviors which are not approved during processing ofthe protected digital content.

As described in more detail below, the present invention employs acombination of techniques, including transaction-time watermarking (orfingerprinting), transaction-time screening, driver software validation,and/or content transfer protection to deter and/or prevent attempts tocircumvent the protection of electronic content. The goal of thesemechanisms is to protect content as much as possible from the time it ispackaged until it is experienced by the consumer.

1. Content Fingerprinting

As described below, in some embodiments a content watermarking orfingerprinting solution may be implemented in the system and/or clientlibrary. For convenience, “watermarking” will be used to refer to themechanism that embeds information in content, whereas a “watermark” willrefer to information that is embedded statically within the content toprovide, for example, an indication of ownership and/or rules forcontent use. A “fingerprint” will generally refer to information that isembedded dynamically, as part of content release, and that (typically)identifies the user who performed the transaction, thus enabling contentto be traced back to the user if, e.g., the content is subsequently usedor distributed in an unauthorized manner. Note that a “watermarking”mechanism can be used to embed either a watermark or a fingerprint,depending on the nature of the information that is embedded.

In one embodiment, a credentialed watermarking engine is used toimplement a predefined interface. Fingerprint attributes are associatedwith content to define the type of technology used to insert thefingerprint and the information to be included therein. An audiofingerprint can be applied at the time content is released, e.g., to aconsumer using a music player application. Techniques for watermarkingvarious types of signals (e.g., audio, visual, textual, etc.) arewell-known in the art, and watermarking technology is readily-availablefrom a variety of companies such as Fraunhofer IIS-A of AmWeichselgarten, 3 D-91058 Erlangen, Germany, and Verance Corporation of6256 Greenwich Drive, Suite 500, San Diego, Calif. (formerly ARISTechnologies, Inc.). Additional watermarking techniques are described orreferenced in Proceedings of the IEEE, Identification & Protection ofMultimedia Information, pp. 1062-1207 (July 1999), and incommonly-assigned U.S. patent application Ser. No. 09/588,652, entitled“Methods and Systems for Encoding and Protecting Data Using DigitalSignature and Watermarking Techniques,” filed Jun. 7, 2000, each ofwhich is hereby incorporated by reference. It should be appreciated,however, that any suitable watermarking and/or fingerprinting techniquemay be used.

Fingerprints can be applied to specific content types based on rules orrequirements specified by content providers. In one embodiment thefingerprints include transaction information to identify the consumer,the content, and/or the transaction itself. Support can be provided forthe use of multiple watermarking technologies, based on content providerrequirements and/or platform/capabilities. In a preferred embodiment ahinted watermarking technique is used to improve the performance offingerprint insertion.

It will be appreciated that fingerprint insertion can be performed in avariety of ways and at a variety of locations in the publishinglifecycle and/or the application's processing chain. For example,fingerprint insertion can be performed by the application and/or byspecialized management software (if present). The application and/ormanagement software may be operable to interact with a watermarkingengine, delivering content to it for fingerprinting and gettingfingerprinted content back. Essentially the same interface can be usedat other points in the chain, either in the client library or in theapplication and/or management software.

1.1. Implementation

FIG. 3 is a block diagram of a system and method for fingerprintingcontent files in accordance with an embodiment of the present invention.As shown in FIG. 3, content provider 302 can define an attribute 350 forcontent objects and/or content streams 304 to specify the type offingerprinting that is to be used. For example, the fingerprintattribute can specify one or more fingerprint rules acceptable to thecontent provider. Each fingerprint rule may specify a watermarkingtechnology and the parameters (which may be null) for use thereby. Theparameters might be in a format dependent on the specific watermarkingtechnology, and may be stored opaquely in the attribute. For example, aparseable ASCII format can be used. In one preferred embodiment, some orall of the following information may be specified:

-   -   Name (or other identifier) of the watermarking engine(s);    -   Specification of the information to be placed in the mark;    -   Parameters describing how the engine(s) should insert the mark;        and    -   Specification of where to find the fingerprinting hints (if        any).        A “null” fingerprinting rule can be placed at the end of the        list to indicate that the content can be released without a        fingerprint if none of the desired engines are available on the        platform.

When access to a content object 304 b is requested by the user, theapplication and/or the management software 320 looks for fingerprintattribute 350 and, if it is present, attempts to find an appropriatewatermarking engine 330 to apply the fingerprint. For example, hooks canbe provided in application or management software 320, and a search forwatermarking engines 330 can be performed in the order specified inattribute 350. A watermarking engine name may specify the name of aloadable module (e.g., a DLL). The module can be loaded by applicationor management software 320, which obtains (and saves) pointers to therelevant interfaces. This can be implemented with the application ormanagement software by defining standard interfaces for watermarkingengines. For example, an initialization interface can be provided, aread interface for fetching marked (output) content, and/or a callbackinterface for fetching unmarked input content.

Application or management software 320 calls the watermarking engine'sinitialization interface with the initialization string specified inattribute 350 and the data to be represented by the fingerprint that theengine will embed. If the call fails, the next fingerprint rule inattribute 350 is attempted. Application or management software 320 setsup the callback interface for communicating with watermarking engine330, and returns from the “content open” call. Subsequent “content read”calls to the application or management software are routed to theengine's read call.

1.2. Hinted Watermarking

In a preferred embodiment, a hinted watermarking technique is used, suchas that described in commonly-assigned U.S. patent application Ser. No.09/629,546, entitled “Software Self-Defense Systems and Methods,” filedJul. 31, 2000, and in commonly-assigned U.S. patent application Ser. No.09/629,807, entitled “Systems and Methods for Watermarking Software andOther Media,” filed Jul. 31, 2000, the relevant sections of which arehereby incorporated by reference. Hinted watermarking techniquestypically break the watermarking or fingerprinting process into at leasttwo separate phases. During the first phase, the unwatermarked contentis processed to identify and/or generate a variety of locations at whichwatermarks or fingerprints can subsequently be inserted. During thesecond phase, the watermarks or fingerprints are actually inserted atthe specified locations. Thus, hinted watermarking allows thecomputationally intensive part of watermarking process to be performedin advance (e.g., at packaging time), thus facilitating the rapidinsertion of watermarks or fingerprints while the content is beingreleased.

A design choice that arises when using a hinted watermarking techniqueis how to package the hints (i.e., the information indicating whereand/or how the fingerprints should be inserted). One approach is toembed the hints in the content stream; another is to store the hints ina separate stream. Embedding the hints in the content stream willtypically be simpler to implement (for both packaging and release), butmay constrain the fingerprinting process to support only onewatermarking engine per content object (except in the somewhat unlikelyevent that two different engines are able to interpret the same hints).In one embodiment, the content analysis and embedding of hints takeplace before the content is sent to the packaging application, thusobviating the need to make changes to the packager.

In a preferred embodiment, watermarking hints are stored in a separatestream (e.g., in attribute 350). This approach supports multiplewatermarking engines for the same content and need not involvepreprocessing of the content itself. It is also potentially more secure,since the hints can be stored separately (especially if the content canever be released without passing through a watermarking engine).However, this approach is also generally more complex, and may requirethe packager to be able to obtain one or more sets of hints and topackage them concurrently with the content (as separate streams).Moreover, on the reading side there will typically need to be multiplecallback interfaces (or at least contexts) to allow the watermarkingengine to fetch the hints. Synchronization will generally be necessary,albeit fairly straightforward to achieve, as the hint stream can be usedto define the synchronization points.

1.3. Watermarking Engine Authentication

In one preferred embodiment credentials are used to authenticate thewatermarking engine to the application and/or management software. Forexample, a valid watermarking engine DLL may be given a credential tocryptographically assure correct identification of the watermarkingengine and to protect against the forgery or substitution ofwatermarking engines. The use of credentials is described more fully inthe Sibert application, previously incorporated by reference herein, andin Menezes et al., Handbook of Applied Cryptography, pp. 543-590 (CRCPress 1996) (“Menezes”), which is hereby incorporated by reference.Moreover, in a preferred embodiment authentication in the otherdirection is provided as well, to prevent unauthorized uses of thewatermarking engine such as the forgery of valid fingerprints or thecreation of illicit fingerprints. Accordingly, in one embodiment thewatermarking engine is operable to establish its own connection to themanagement and/or application software, and to use that connection tovalidate the credential of its caller.

For additional security, the data that are passed across thewatermarking engine interface (e.g., data passing across the interfacefor raw content and/or data passing across the interface for markedcontent) may be encrypted. In one embodiment, a relatively lightencryption (e.g., Diffie-Hellmann) with a key negotiated during engineinitialization is used. However, in other embodiments, lesser (orgreater) levels of protection could be used.

2. Module Validation

In one embodiment the modules that are involved in handling content(e.g., drivers, plug-ins, and/or components) are checked to determinewhether they behave in a satisfactory manner. This process generallyinvolves identifying and validating the content-handling modules (e.g.,both application driver modules 220 a and kernel driver modules 220 b),as well as responding to the results of the identification/validationprocess.

2.1. Identification and Validation

In a preferred embodiment a library of identification and validationinformation is maintained for use in the identification and validationprocess. For example, drivers can be identified or validated in a numberof ways, including without limitation by their file names; bycryptographic signatures contained in the drivers; by distinctive codepatterns and/or behavior patterns contained in, or exhibited by, thedrivers; by the size of the driver files; by the memory (and/orhardware) addresses at which the drivers are located; or by any othersuitable technique, including a combination of some or all of theaforementioned identification techniques.

In one embodiment the identification and validation process is performedby inspector modules 230 operating in conjunction with inspectionmanager software 232, as shown in FIG. 2. Inspector modules are operableto check the structure and/or behavior of drivers, software, and/orhardware against predefined criteria and to report the results of thesechecks to inspection manager software 232. For example, in oneembodiment the inspector module is a daemon process that is triggered bythe system interrupt (e.g., INT 03) that is generated when drivers areloaded to process content. Thus, the inspector module is able todetermine the identity of the drivers that are actually used to processthe content, and can then locate the drivers' corresponding registryentries and/or compute the cryptographic hash of the drivers and compareeach hash value with a list of known good (or known bad) drivers, orperform other analysis, as described in more detail elsewhere herein.

In a preferred embodiment inspectors 230 and inspection manager 232 aregiven credentials. The credentials contain attributes specifying theinspector's or manager's identity, which calling software (such as anapplication) can verify to be sure it matches the intended identity, inorder to protect against the forgery or substitution of inspectors 230and/or inspection managers 232. Moreover, it will be appreciated thatwhile for ease of explanation inspectors 230 and inspection managersoftware 232 are described as separate entities, in some embodimentsinspectors 230 and inspection management software 232 may form part of asingle software module. For example, inspectors 230 and inspectionmanagement software 232 may comprise an independent software module, orcan be included within application software 214 or management software216. For example, in one embodiment the functionality described above isobtained by integrating a shim API to the system's multimedia managementsystem DLL into the application, the shim API being operable to routecalls to the system DLL to the inspection manager software 232, which isoperable to evaluate the drivers identified and/or analyzed byinspectors 230 and to take appropriate action before forwarding theoriginal call to the system DLL. In other embodiments, some or all ofinspectors 230 and/or inspection management software 232 can beimplemented in hardware.

FIGS. 4A and 4B are flow charts illustrating the operation of inspectormodules 230 in embodiments of the present invention. Referring to FIG.4A, in one embodiment each inspector module 230 is operable, uponreceipt of an appropriate command from inspection manager software 232,to locate drivers in the appropriate driver chain (410), to inspectthose drivers using predefined criteria (such as those set forth above)(420), and to send the results of the inspection to inspection manager232 (430). As shown in FIG. 4B, in other embodiment inspectors 230complete inspection of each driver in a driver chain before reportingback to the inspection manager. In other embodiments other reportingprotocols may be used.

As shown in FIG. 5, inspectors 230 may have access to one or more listsof criteria 520 against which to check driver modules 530. For example,lists 520 might include one or more public keys used to verify thecryptographic signatures, if any, contained within driver modules 530.In one embodiment, the integrity of lists 520 is maintained using acombination of cryptographic and obfuscatory techniques, as described,e.g., in the '900 and '422 patents and the Shear and Collbergapplications.

Identification information can be stored regarding the drivers residingin the kernel memory space and the user memory space. It will beappreciated that ring zero driver modules are typically fairly easy toidentify due to the WINDOWS kernel structures that tie them together instacks. However, it will also be understood that the kernel structuresdiffer between WINDOWS NT, WINDOWS 95, WINDOWS 98, and WINDOWS 2000.Application plug-in modules, on the other hand, are typically tiedtogether in an application-defined structure.

In a preferred embodiment only those drivers that are involved in theprocessing of the content are taken into account, since even ifunacceptable driver modules are present in the system, they typically donot pose a threat to the content unless they are actually involved inprocessing it. However, in a preferred embodiment the modules that arebeing used are dynamically monitored in order to track changes made tothese modules during system operation. For example, if it is possiblefor a module to adjust the stack after the first check is made, thecheck is made again. In one embodiment inspectors 230 are integratedwith the operating system software such that they can detect allregistered drivers.

Some modules can be continuously monitored by hooking the functions thatload and unload them. This can be done by a monitoring function thatstarts at boot time and watches continuously. However, boot-time orcontinuously resident mechanisms may introduce reliability problems, dueto the increased chance of failure that is typically characteristic ofsuch mechanisms, and because of the possibility of interference withother continuously resident mechanisms like virus scanners. Thus, in oneembodiment the module structures are validated in-place at the time thecontent is processed.

2.1.1. Validation by Implicit Identification (Signature)

In a preferred embodiment credential/certification techniques describedin the Sibert application and the Menezes reference, previouslyincorporated herein by reference, are used in conjunction with thedriver/module validation mechanisms described above to authenticatecertified code that has been marked as trusted, thus reducing thecomplexity of the processing necessary to reliably discriminate betweenmalicious and approved behaviors. This is an important capability, asthe general techniques available to malicious programs are virtuallyunbounded. However, the body of code which can be proven as trustworthyis also virtually unbounded, due to the fact that it may be developed bymany different companies, in many different places, and/or may bereleased in many different versions over the lifetime of any given pieceof digital content. It is therefore an advantage of embodiments of thepresent invention to incorporate the ability to differentiate known,trusted code from non-trusted code, and to be able to incorporate thisinformation in the process of detecting malicious behaviors.

In one embodiment a check can be made for a digital signature on thedevice or filter module, the signature confirming that the moduleoriginated from a trustworthy party. For example, the validationfunction could implement a rule saying that all drivers signed by aparticular party are implicitly acceptable, even though the validationfunction may not have other specific knowledge about any specific one ofthese drivers. The MICROSOFT® AUTHENTICODE infrastructure, for example,can be used to support such usage. However, it should be appreciatedthat any suitable signature or identification technique could be used inaccordance with the principles of the present invention, including,e.g., those described in Schneier, Applied Cryptography, 2d ed., pp.483-512 (John Wiley & Sons 1995), which is hereby incorporated byreference. In a preferred embodiment, the validation system contains alist of acceptable signers, which can be updated and/or replaced by atrusted third party, such as the provider of the system's managementsoftware. In one embodiment, the list can be automatically updated usingtechniques described in the '019 and '900 patents and in the Sibertapplication, previously incorporated by reference herein.

2.1.2. Validation by Explicit Identification

In addition to implicit validation by digital signatures, acryptographic hash of the module's code can be compared against lists ofhash values for “known good” and “known bad” modules. In one embodiment,a trusted party periodically distributes digitally-signed lists of hashvalues, where each hash has an associated “good” or “bad” attribute. Theinspection process hashes the binaries it encounters and looks up thehashes in the list(s), which can be sorted for enhanced efficiency. Itshould be appreciated that a single list of all “known” modules could beused instead (rather than a sequence of lists). This list could beupdated periodically through an automated update mechanism, such as thatdescribed above. Moreover, it should be appreciated that any suitablehashing technique could be used, including, e.g., those described inSchneier, Applied Cryptography, 2d ed., pp. 429-459 (John Wiley & Sons1995), which is hereby incorporated by reference.

2.1.3. Validation by Scanning

Identifying known modules by hash values is fine for “good” modules, buta “bad” module could be trivially altered (by its creator) to have adifferent hash, and thus escape detection by such a scheme. Thus, in apreferred embodiment, more sophisticated scanning techniques are alsoused. For example, to identify a module (e.g., a kernel and/orapplication driver or filter) as “probably unacceptable,” some or all ofthe following heuristic approaches can be used:

-   -   For some types of modules (e.g., ring zero drivers), there will        typically be a rather limited set of system interfaces that such        a module can legitimately invoke. Thus, the presence of imports        for other interfaces can serve as an indicator of undesirable        behavior. Such a scan can be performed statically on the        module's code, dynamically while the module is running, or both.        However, such a scan may be defeatable by code that develops        function pointers internally, rather than by using imports.    -   Alternatively, or in addition, a list of interfaces that are        known to be undesirable can be maintained. Although this        approach is generally not as robust as a restrictive list, in        some applications it may be more acceptable from an end-user        standpoint because it will result in fewer false hits. For audio        content, for example, known undesirable interfaces include file        I/O, network I/O, and various other forms of IPC, such as DDE.    -   Yet another approach is to scan for code sequences that are        known (or suspected) to represent undesirable behavior—for        example, code that attempts to develop function pointers, or        strings holding the literal names of undesirable interfaces.    -   Another approach is to identify “signature” sequences from        “known bad” modules and to scan for them, similar to the manner        in which anti-virus programs identify and scan for such        sequences in computer viruses. This approach has the advantage        that even if changes are made to the “known bad” modules, there        will typically be much in common between the old and the new        versions, and thus “known bad” modules will have a more        difficult time evading detection.    -   Yet another approach is to monitor and analyze the dynamic        timing operations performed by the module to identify anomalous        timing characteristics indicative of invalid and/or malicious        activities. For example, a normal request to a hardware        peripheral may take a known amount of time. Thus, if the request        takes significantly longer to complete, it may indicate that        additional (potentially malicious) processing is occurring in        the driver chain. Similarly, if the request takes significantly        shorter to complete, it may indicate the absence of necessary        (potentially protective) processing in the driver chain.

In one embodiment, a scan is performed for patterns of op-code bytesseparated by “don't care” bytes, where the “don't care” bytes cover theaddress and offset portions of instructions. This approach is based onthe fact that changes elsewhere in the code are likely to changeaddresses, but are unlikely to change the basic algorithms. If a handfulof locations (e.g., 20) are randomly chosen within the binary, andrelatively small signatures (e.g., 50 bytes) are generated for thoselocations, they can serve to identify a particular program. Even if theprogram is modified and recompiled, most of the signatures willtypically be preserved, thus enabling the system to treat it as a hit,for example, if only 18 of 20 signatures are found (or any othersuitable predefined number). Potential signatures can be located bydisassembling the binaries with TracePoint to locate the instructions;this has the advantage of allowing signatures to be chosen that arecontained in a single function. It is also possible to use statisticaltechniques to identify opcodes. While such an approach is typically lessreliable in terms of signature identification, it is easier to implementand less fragile.

Signatures are preferably sorted or otherwise organized such that asingle scan through any particular binary can simultaneously check allsignatures. Moreover, the scanning parameters (especially specificsequences), like the hash values, are preferably distributed and updatedautomatically. In a preferred embodiment, the “known good” listmechanism is combined with a scanning mechanism, thus giving the systema way of accepting modules that for some spurious reason fail the scan,but are actually legitimate.

2.1.4. Policy-Based Validation

In one preferred embodiment the monitoring and detection functions, andthe response to identified malicious behaviors, are under the control ofan application or associated DRM services policy. Such a policy can bemapped in a relatively straightforward manner to the processing rulesassociated with the protected digital content itself. (The associationof content and rules is described in the '019 and '900 patents,previously incorporated by reference herein).

In a preferred embodiment the detection and monitoring system is invokedat the time that a piece of digital content is selected for processingand its rules have been established. If the rules allow the content tobe saved to local storage, the detection and monitoring system need onlyinspect the processing chain to determine whether there are any attemptsin progress at the start of processing, or during ongoing transfer ofthe content, to direct it through a redirected or substitute module. Ina preferred embodiment, additional markings may be added to the contentstream in order to allow instrumentation of the general driver stack forthe storage medium, or another port capable of streaming the content, inorder to determine if the content is being directed through anunapproved streaming channel. Similarly, if the rules associated withthe content allow the content to be presented only on screen (e.g.“view”), or to be played only through an audio device (e.g., “play”),then the detection and monitoring system need only set-up processeswhich instrument the channels appropriate to detecting attacks againstthose functions (e.g. storing content for later playback, directing itthrough a substitute module or redirected interface to defeat theprotection mechanisms, etc.).

In each of these examples, the protection mechanism is invoked andconfigured according to the policies of the application, based on rulesassociated with the digital content. The techniques described can beeffectively independent of other protections provided by the operatingsystem on which the application or its associated DRM system is running.This is an important feature, since, in general, there is no objectiveconsistency to the access control semantics or guarantees affordeddigital content as it may be used on different operating systems andtheir native protections. Accordingly, embodiments of the presentinvention may optionally incorporate additional support from someoperating systems, but need not be entirely reliant on protection oraccess control mechanisms afforded by the operating system, as policiesare preferably a function of the rules encoded and associated with thecontent itself.

In a preferred embodiment, the implementation of the policies specifiedby the application, content provider, and/or management software ishandled by policy enforcement manager 234, as shown in FIG. 2. Policyenforcement manager 234 interacts with inspection manager 232 to obtainthe results of the inspectors' analysis of relevant driver, software,and/or hardware modules. Using these results, policy enforcement manager234 implements the specified policy or policies. In a preferredembodiment, policy enforcement manager, like inspection manager 232 andinspectors 230, is credentialled.

FIG. 5 illustrates the implementation and application of a policy in oneembodiment of the present invention. Referring to FIG. 5, managementsoftware 216 retrieves digital content from an external source, such ashard disk drive 110 or network 136, via a secure container 510. Securecontainer 510 may contain digital content file 512, rules 514 governingthe use of content 512, and policy criteria 516 governing the securityto be applied while using the content in accordance with rules 514.Digital container 510 may, for example, be implemented and used inaccordance with the techniques described in the '900 and '019 patents.In a preferred embodiment, secure container 510 comprises a DIGIBOX®container produced by InterTrust Technologies Corporation of SantaClara, Calif., and management software 216 comprises INTERRIGHTS POINT™digital rights management software, also produced by InterTrust. Inother embodiments, other management software and/or secure container orfile mechanisms are used.

Management software 216 is operable to release content file 512 fromcontainer 510 to application software 214 in accordance with the rules514 that govern the content's use. For example, management software 216may release content 512 to application software 214 upon receipt of apredefined payment from the user. The operation of management software214 in preferred embodiments of the present invention is described inmore detail in the '900 and '019 patents.

Policy criteria 516 may be specified by the content provider, by theapplication developer, and/or by the developer or controller of themanagement software. In one embodiment, participants in the value chainare not allowed to circumvent the policies specified by more seniorvalue chain members (see, e.g., the '900 patent for a discussion ofvalue chains). For example, the application developer may be unable(without the content owner's consent) to apply a lesser level ofsecurity (e.g., enforce a less restrictive set of policy criteria) thanthe level of security specified by the content owner. The applicationdeveloper may, however, be allowed to enforce a stricter set of policycriteria than that specified by the content owner.

Upon releasing content file 512 from container 510, management software216 also releases policy criteria 516 to policy enforcement manager 234,inspection manager 232, and/or inspectors 230, where these criteria areintegrated with the default policies (if any) specified by applicationsoftware 214 and/or management software 216. Inspectors 230 then usethese policy criteria to inspect the appropriate drivers, and to reportthe results of their inspection to inspection manager 232 and/or policyenforcement manager 234, which evaluate the security of the system byapplying the policy to the inspection data. If the results of thisanalysis indicate that defensive action is warranted, an appropriatesignal is sent to application 214 and/or management software 216.

FIG. 6 provides an example of the application of a policy to the dataobtained by inspectors 230. As shown in FIG. 6, policy enforcementmanager 234 may contain a variety of different policies 604 associatedwith a given piece of electronic content. For purposes of illustration,FIG. 6 shows two such policies 604, one governing the release of acontent file to a printer, the other governing the release of thecontent file to a disk drive. As shown in FIG. 6, the policies maycomprise logical expressions containing a variety of conditions. Forexample, print policy 604 a indicates that the content file can be sentto the printer as long as (a) the rules (e.g., rules 514 in FIG. 5)associated with the content indicate that it is ok to print the content(i.e., if the print intent is enabled); and (b) the drivers responsiblefor handling the content on its way to the printer satisfy certainconditions (e.g., a certain percentage have valid signatures, certaindrivers' hash values are found on the list of known “good” drivers,etc.). Inspectors 230 gather the data 602 needed by policy enforcementmanager 234 to evaluate the logical policy expressions 604. For example,inspectors 230 might check the cryptographic signatures (if any)associated with the drivers in the appropriate driver chain, compute thehash of a driver and compare it to lists of known “good” and/or known“bad” drivers, compute the checksum of all or part of a driver, checkfor calls to certain interfaces such as disk I/O, and/or perform avariety of other data gathering and analysis operations. Upon receivinginspection data 602, policy enforcement manager 234 is operable todetermine whether the appropriate policy criteria 604 have beensatisfied, and permit the release of the content and/or take appropriatedefensive action accordingly.

In one embodiment, driver modules are classified within one of threegeneral categories: modules that are unambiguously acceptable, modulesthat are unambiguously unacceptable; and modules that are probablyunacceptable (or acceptable). However, it will be appreciated that avirtually limitless number of policies could be implemented inaccordance with the principles of the present invention.

In a preferred embodiment, the techniques described in the '900 and '019patents for independently delivering rules and controls are applied toenable policy criteria to be independently updated. For example, if itbecame known that the security of the drivers manufactured by aparticular party had been compromised, the content owner, applicationdeveloper, and/or rights management software operator could modify thepolicies associated with susceptible content to indicate that thecontent should not be used in conjunction with drivers containing thecompromised party's signature. When a secure driver was developed toreplace the compromised one, the policies associated with thesusceptible content could be modified once again to allow usage of thenew driver. Thus, the security of the system can be flexibly andseamlessly controlled without the need for entire content files to beretransmitted, or application programs rewritten and re-released,whenever changes in policy are desired.

While management software 216, application software 214, policyenforcement software 234, inspection manager 232, and inspectors 230are, for ease of explanation, shown in FIG. 5 as separate modules, itshould be appreciated that this need not be the case. For example, oneof ordinary skill in the art will appreciate that some or all of thesemodules can be combined with each other without departing from theprinciples of the present invention.

2.1.5. Interlocking Identification and/or Validation

In one embodiment the content protection mechanisms described above canbe linked with, and can be tested for, authenticity by the applicationand/or its associated DRM system. For example, the code that implementsthe protection mechanism can be authenticated using techniques such asthose described in the Sibert application, the '900 patent, or theMenezes reference. In such an embodiment the application program or DRMsystem is thus able to determine whether the protection mechanism can betrusted. In one embodiment the application and/or its associated DRMsystem is linked with the protection mechanism using standardlinker/loader techniques, and is instrumented by the application or DRMprogrammer to ensure that the protection mechanism is loaded andrunning. An application so instrumented can also be certified by abusiness process associated with the use of the protection mechanism,such that a certified application will not run if the protectionmechanism is disabled. Different program modules running in user modeand/or kernel mode operating system memory can be similarly instrumentedto perform ongoing checks for the presence of authentic and credentialedcode. If any part of the protection mechanism is disabled, allinstrumented code can be made to discontinue processing.

2.2. Response

When an unacceptable module is detected during processing of protectedcontent, the system is operable to respond in an appropriate manner. Forexample, in one embodiment three response options are provided: (1)return an error and deny the operation; (2) remove or disable theoffending module and deny the operation; and (3) damage the content, butpermit the operation to continue.

For example, upon detecting an unacceptable driver module, the systemcan inform the user that the content is not accessible because theoffending driver is present in the user's configuration. A moresophisticated response is to remove or disable the unacceptable module.This is particularly plausible for drivers, where there are well-definedinterfaces for doing so; however, will generally be undesirable to havea tamper-resistance mechanism change the configuration of drivers in thesystem, as pushing and popping drivers dynamically might interfere withother legitimate uses of those drivers, and might also carry anon-negligible risk of crashes.

Another form of response involves damaging the content, but stillallowing it to be processed. From a countermeasures standpoint, thiswill typically be better than simply preventing access to the content,as it will generally be more difficult for a hacker to recognize andundo damage, or to prevent it from happening, than it is to identify adecision point that prevents the access entirely. Damage can involve anysuitable mechanism, including those as simple as randomly changing bitsin the stream without an understanding of the content semantics, or canbe more sophisticated, involving, e.g., the removal of high-frequencycomponents from audio data.

3. Content Transfer Protection

Embodiments of the present invention may also incorporate a novelcontent transfer protection mechanism. The content transfer protectionmechanism works by generating content “signatures” or identifiers forprotected content, then filtering file system interfaces (and/or othercommunication interfaces, including without limitation network andinter-process communication interfaces) to prevent the writing of datacontaining those signatures or identifiers. In this context, a contentsignature is preferably a distillation (similar to a secure hash) ofsome part of a protected content object. In a preferred embodiment thesignature is derived from the content, as opposed to being inserted intothe content like a watermark. For example, the MD4 hash algorithm couldbe used to generate an identifier consisting of the hash of some or allof the content object. As yet another example, the identifier mightsimply consist of a predefined portion of the content object (e.g., asegment of 512 bytes). In other embodiments, other identificationschemes can be used. The content signature mechanism may be optimizedfor rapid scanning to locate signatures within large sequences of data.

FIGS. 7A, 7B, and 8 illustrate a content transfer protection mechanismin accordance with an embodiment of the present invention. As shown inFIGS. 7A and 8, when content 802 is released by the management software803 to an application 804, transfer manager 810 (which may, in someembodiments be integrated with the application and/or managementsoftware library) derives one or more signatures 811 from the content(blocks 710-712 in FIG. 7A). In one embodiment, the signature of thefirst 512 bytes of content is taken, as are the signatures of predefinedselections of subsequent 512-byte blocks. As transfer manager 810generates each signature 811, it informs the transfer protectionmonitors 812 of the signature's value (block 714 of FIG. 7A). In oneembodiment, monitors 812 maintain a list of such signatures.

Referring to FIGS. 7B and 8, transfer protection monitors 812, which mayoperate as kernel drivers within the operating system, intercept databeing written through file (or other) system interfaces and scan thesedata for signatures 811 in the specified list of values (blocks 750-752in FIG. 7B). If a matching region of data is found (i.e., a “yes” exitfrom block 754), and it is being written to an invalid destination,corrective action can be taken (756). For example, content file 802 inFIG. 8 is only allowed to be viewed on monitor 818 (as specified byrules 807 associated with content file 802). Thus, if content file 802is sent to printer 820 or to disk storage 830, monitors 812 will detectit and take defensive action (denoted in FIG. 8 by Xs blocking thedriver paths). The defensive action may simply be to make the operationfail, or it may instead be to damage the data so that the resulting fileis not obviously broken, but has internal damage that effectivelyeliminates its commercial value (e.g., the content could be scrambled).

One of ordinary skill in the art will recognize that the systems andmethods presented herein are readily applicable to a wide variety ofcontent types and applications. For example, the systems and methods ofthe present invention can be used to enhance the security of printing orviewing content files. Although printer drivers can legitimately includefile I/O calls, and thus should generally not be scanned to avoid them,scanning can be used to prevent the use of certain unacceptable printdrivers. Moreover, while print jobs are often written to print queuefiles which cannot be readily protected, locally-accessible print queuescan be created to address this problem. In addition, certain print spoolentries can be intercepted and encrypted/decrypted as appropriate. Yetanother protection that can be applied is to disable, at the driverinterface level, the ability to print to a file and/or to requestmultiple copies of a printout.

Although the foregoing invention has been described in some detail forpurposes of clarity, it will be apparent that certain changes andmodifications may be practiced within the scope of the appended claims.It should be noted that there are many alternative ways of implementingboth the processes and apparatuses of the present invention.Accordingly, the present embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalents of the appended claims.

What is claimed is:
 1. A computer-implemented method for protectingelectronic content from unauthorized use by a computer system, themethod comprising: receiving a request to process electronic contentusing a software module executing on the computer system; obtaining afirst identifier associated with the software module, wherein the firstidentifier is a distillation of some part of the software module;comparing the first identifier with a second identifier; determiningthat the first identifier is related to the second identifier in apredefined manner, and that the software module exhibits one or morepredefined behaviors, wherein the determination that the software moduleexhibits one or more predefined behaviors includes detecting at leastone of: the software module attempting to access one or more predefinedsystem interfaces, and the software module exhibiting one or morepredefined timing characteristics; and implementing at least one actionto protect the electronic content from unauthorized use based on thedetermination.
 2. The method of claim 1, wherein the software modulecomprises one or more system drivers.
 3. The method of claim 1, whereinthe one or more system drivers comprises at least one of a video displaydriver, a sound driver, an SCSI driver, an IDE driver, a network driver,a video capture driver, a floppy disk driver, and a scanner driver. 4.The method of claim 1, wherein the at least one action comprisesmodifying at least a portion of the electronic content before it isprocessed by the software module.
 5. The method of claim 4, whereinmodifying at least a portion of the electronic content comprisesscrambling at least a portion of the electronic content.
 6. The methodof claim 4, wherein modifying at least a portion of the electroniccontent comprises adding noise to at least a portion of the electroniccontent.
 7. The method of claim 4, wherein modifying at least a portionof the electronic content comprises adding an electronic watermark to atleast a portion of the electronic content.
 8. The method of claim 1,wherein the at least one action comprises preventing the software modulefrom processing the electronic content.
 9. The method of claim 1,wherein the electronic content comprises electronic media content. 10.The method of claim 1, wherein the first identifier comprises a hashvalue of at least a portion of the software module and the secondidentifier comprises one or more known hash values.
 11. The method ofclaim 10, wherein the one or more known hash values comprise one or morehash values of one or more known unauthorized software modules.
 12. Themethod of claim 1, wherein obtaining the first identifier, comparing thefirst identifier with the second identifier, and determining that thefirst identifier is related to the second identifier in a predefinedmanner are performed according to one or more policies associated withthe electronic content.
 13. A non-transitory computer-readable storagemedium storing instructions that, when executed by a processor of acomputer system, cause the computer system to perform a methodcomprising: receiving a request to process electronic content using asoftware module executing on the computer system; obtaining a firstidentifier associated with the software module, wherein the firstidentifier is a distillation of some part of the software module;comparing the first identifier with a second identifier; determiningthat the first identifier is related to the second identifier in apredefined manner, and that the software module exhibits one or morepredefined behaviors, wherein the determination that the software moduleexhibits one or more predefined behaviors includes detecting at leastone of: the software module attempting to access one or more predefinedsystem interfaces, and the software module exhibiting one or morepredefined timing characteristics; and implementing at least one actionto protect the electronic content from unauthorized use based on thedetermination.
 14. The non-transitory computer-readable storage mediumof claim 13, wherein the software module comprises one or more systemdrivers.
 15. The non-transitory computer-readable storage medium ofclaim 13, wherein the at least one action comprises modifying at least aportion of the electronic content before it is processed by the softwaremodule.
 16. The non-transitory computer-readable storage medium of claim13, wherein the at least one action comprises preventing the softwaremodule from processing the electronic content.
 17. The non-transitorycomputer-readable storage medium of claim 13, wherein the firstidentifier comprises a hash of at least a portion of the software moduleand the second identifier comprises one or more known hash values. 18.The non-transitory computer-readable storage medium of claim 17, whereinthe one or more known hash values comprise one or more hash values ofone or more known unauthorized software modules.
 19. The non-transitorycomputer-readable storage medium of claim 13, wherein obtaining thefirst identifier, comparing the first identifier with the secondidentifier, and determining that the first identifier is related to thesecond identifier in a predefined manner are performed according to oneor more policies associated with the electronic content.
 20. Thenon-transitory computer-readable storage medium of claim 13, wherein theelectronic content comprises electronic media content.